Method for manufacturing light guide elements

ABSTRACT

Systems and methods described herein relate to the manufacture of optical elements and optical systems. An example method includes overlaying a first mask on a photoresist material and a substrate, and causing a light source to illuminate the photoresist material through the first mask during a first exposure so as to define a first feature. During the first exposure, the light source is positioned at a non-normal angle with respect to a plane parallel to the substrate. The method includes developing the photoresist material so as to retain an elongate portion of the photoresist material on the substrate. A first end of the elongate portion includes an angled portion that is sloped at an angle with respect to a long axis of the elongate portion. The method also includes depositing a reflective material through a second mask onto the angled portion.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. patent application Ser. No.16/684,955 filed Nov. 15, 2019 which is a continuation of U.S. patentapplication Ser. No. 15/794,966 filed Oct. 26, 2017, the contents ofboth of which are incorporated herein by reference in their entirety.

BACKGROUND

Unless otherwise indicated herein, the materials described in thissection are not prior art to the claims in this application and are notadmitted to be prior art by inclusion in this section.

Light guiding devices may include optical fibers, waveguides, and otheroptical elements (e.g., lenses, mirrors, prisms, etc.). Such lightguiding devices may transmit light from an input facet to an outputfacet via total or partial internal reflection. Furthermore lightguiding devices may include active and passive optical components, suchas optical switches, combiners, and splitters.

Optical systems may utilize light guiding devices for a variety ofpurposes. For example, optical fibers may be implemented to transmitoptical signals from a light source to a desired location. In the caseof light detection and ranging (LIDAR) devices, a plurality of lightsources may emit light, which may be optically coupled to the lightguiding devices so as to be directed into a given environment. The lightemitted into the environment may be detected by a receiver of the LIDARdevices so as to provide estimated distances to objects in theenvironment.

SUMMARY

Systems and methods described herein are applicable to the manufactureof optical systems. For example, the present disclosure describescertain optical elements (e.g., light guide devices) and methods fortheir manufacture.

In a first aspect, a method is provided. The method includes depositinga photoresist material on a substrate and overlaying a first mask on thephotoresist material, wherein the first mask defines a first feature.The method additionally includes causing a light source to illuminatethe photoresist material through the first mask. The light source ispositioned at a first angle. The first angle includes a non-normal anglewith respect to a plane parallel to the substrate. The method alsoincludes developing the photoresist material so as to retain an elongateportion of the photoresist material on the substrate. A first end of theelongate portion includes an angled portion. The angled portion issloped at an angle with respect to a long axis of the elongate portion.The method yet further includes overlaying a second mask on thedeveloped photoresist material. The second mask defines a second featurecorresponding to the angled portion. The method includes depositing areflective material through the second mask onto the angled portion.

In a second aspect, a method is provided. The method includes depositinga photoresist material on a substrate and overlaying a first mask on thephotoresist material, wherein the first mask defines a first feature.The method also includes overlaying a second mask on the first mask. Thesecond mask defines a second feature. The method additionally includescausing a light source to illuminate the photoresist material throughthe first mask and the second mask. The light source is positioned at afirst angle. The first angle includes a non-normal angle with respect toa plane parallel to the substrate. The method also includes removing thesecond mask and overlaying a third mask on the first mask. The thirdmask defines a third feature. The method yet further includes causingthe light source to illuminate the photoresist material through thethird mask and the first mask. The method additionally includesdeveloping the photoresist material so as to retain an elongate portionof the photoresist material on the substrate. A first end of theelongate portion includes an angled portion. The angled portion issloped at an angle with respect to a long axis of the elongate portion.The method also includes overlaying a fourth mask on the developedphotoresist material. The fourth mask defines a fourth feature tocorrespond to the angled portion The method yet further includesdepositing a reflective material through the fourth mask onto the angledportion.

Other aspects, embodiments, and implementations will become apparent tothose of ordinary skill in the art by reading the following detaileddescription, with reference where appropriate to the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A illustrates an optical element, according to an exampleembodiment.

FIG. 1B illustrates optical elements, according to example embodiments.

FIG. 1C illustrates an optical element, according to an exampleembodiment.

FIG. 1D illustrates an optical system, according to an exampleembodiment.

FIG. 1E illustrates an optical system, according to an exampleembodiment.

FIG. 1F illustrates an optical system, according to an exampleembodiment.

FIG. 2A illustrates a block of a method of manufacture, according to anexample embodiment.

FIG. 2B illustrates a block of a method of manufacture, according to anexample embodiment.

FIG. 2C illustrates a block of a method of manufacture, according to anexample embodiment.

FIG. 2D illustrates blocks of a method of manufacture, according toexample embodiments.

FIG. 2E illustrates a block of a method of manufacture, according to anexample embodiment.

FIG. 2F illustrates a block of a method of manufacture, according to anexample embodiment.

FIG. 2G illustrates a block of a method of manufacture, according to anexample embodiment.

FIG. 2H illustrates a block of a method of manufacture, according to anexample embodiment.

FIG. 2I illustrates a block of a method of manufacture, according to anexample embodiment.

FIG. 2J illustrates a block of a method of manufacture, according to anexample embodiment.

FIG. 2K illustrates a block of a method of manufacture, according to anexample embodiment.

FIG. 3 illustrates a method, according to an example embodiment.

FIG. 4 illustrates a method, according to an example embodiment.

DETAILED DESCRIPTION

Example methods, devices, and systems are described herein. It should beunderstood that the words “example” and “exemplary” are used herein tomean “serving as an example, instance, or illustration.” Any embodimentor feature described herein as being an “example” or “exemplary” is notnecessarily to be construed as preferred or advantageous over otherembodiments or features. Other embodiments can be utilized, and otherchanges can be made, without departing from the scope of the subjectmatter presented herein.

Thus, the example embodiments described herein are not meant to belimiting. Aspects of the present disclosure, as generally describedherein, and illustrated in the figures, can be arranged, substituted,combined, separated, and designed in a wide variety of differentconfigurations, all of which are contemplated herein.

Further, unless context suggests otherwise, the features illustrated ineach of the figures may be used in combination with one another. Thus,the figures should be generally viewed as component aspects of one ormore overall embodiments, with the understanding that not allillustrated features are necessary for each embodiment.

I. Overview

Systems and methods described herein relate to the manufacture ofelements of an optical system. Namely, various processing techniquescould be utilized to form one or more light guides of the opticalsystem. The light guides could include an elongate portion that extendsalong a surface of a substrate. The light guides may also include anangled portion coated with a metal that is optically reflective. In anexample embodiment, the light guides may be formed from SU-8 resist andmay be configured to guide infrared light.

Processing techniques to form the one or more light guides describedherein may include performing a double exposure of a photoresist. Forexample, a first exposure may be made at a near-normal angle and thesecond exposure may be provided at an oblique angle with respect to thephotoresist surface. The double exposure may help provide the angledportion due to an angled dose profile. Optionally, one or both exposuresof the double exposure method could be performed using immersionlithography.

Another processing technique described herein includes a “blur mask”approach, which may be utilized when two photomasks are overlaid on thesubstrate at the same time. A first exposure may be performed throughthe two photomasks. Subsequently, the top photomask could be changed outfor a photomask that provides a different pattern of openings onto thesubstrate. In such a scenario, a second exposure could be performed,which may provide a controllable dose profile. The controllable doseprofile may be adjusted to form the angled portion of the light guide.

In yet another processing technique, UV light could be controllably“painted” through a slit or another type of aperture and may expose thephotoresist-covered substrate at an oblique angle. In such a scenario,the corresponding dose profile may be angled, which may be utilized toprovide the angled portion of the light guide. In further embodiments,fabrication methods for producing light guides may include variouscombinations of the above-mentioned processing techniques.

II. Example Optical Elements and Optical Systems

FIG. 1A illustrates an optical element 100, according to an exampleembodiment. In some cases, the optical element 100 may be formed from apolymeric material, such as photoresist. For example, the polymericmaterial may include SU-8 polymer, Kloe K-CL negative photoresist, DowPHOTOPOSIT negative photoresist, or JSR negative tone THB photoresist.It will be understood that the optical element 100 may be formed fromother polymeric photo-patternable materials.

In some embodiments, the optical element 100 may include an elongatestructure. The elongate structure may include a first light guideportion 102 and a second light guide portion 104. The second light guideportion 104 may be wider in at least one dimension than the first lightguide portion 102. In an example embodiment, the optical element 100 mayinclude an angled portion 110. The optical element 100 may additionallyinclude a first end facet 106 and a second end facet 108. While FIG. 1Aillustrates the optical element 100 as having a certain shape, othershapes are possible and contemplated herein.

In example embodiments, the optical element 100 may be configured toguide light. For example, optical element 100 may be configured tocouple light from a light source via the first end facet 106. Such lightmay be guided within at least a portion of optical element 100 via totalinternal reflection. In some embodiments, at least a portion of thelight may be coupled out of the optical element via second end facet108.

FIG. 1B illustrates optical elements 100 a and 100 b, according toexample embodiments. Optical element 100 a may be similar to opticalelement 100. For instance, the optical element 100 a may include a firstlight guide portion 102 and a second light guide portion 104, and anangled portion 110. The optical element 100 a may also include a firstend facet 106 and a second end facet 108. In some embodiments, a width112 of first light guide portion 102 may be smaller than a width 114 ofa second light guide portion 104.

Optical element 100 b could be similar to optical element 100. Forexample, optical element 100 b may include a light guide portion 105, anangled portion 110 and an end facet 109. The optical systems and methodsof manufacture described herein may include optical elements 100, 100 a,and/or 100 b.

In some embodiments, the angled portion 110 of the optical elements 100,100 a, and 100 b may include a reflective material. For example, theangled portion 110 may include a metallic coating. In some embodiments,the metallic coating may include one or more metals such as titanium,platinum, gold, silver, aluminum, and/or another type of metal. In someother embodiments, the angled portion 110 may include a dielectriccoating and/or a dielectric stack.

FIG. 1C illustrates an optical element 120, according to an exampleembodiment. Optical element 120 may be similar or identical to opticalelement 100 as illustrated and described in relation to FIG. 1A. In anexample embodiment, a light source 122 may emit light that may becoupled (e.g., via a first end facet 106) into a first light guideportion 102 as coupled emission light 124. The coupled emission light124 may be outcoupled to an environment via a second end facet 108. Theoutcoupled light may include transmitted light 126, which may interactwith objects in the environment (e.g., via reflection, absorption,and/or refraction). At least a portion of the transmitted light 126 maybe reflected or otherwise redirected toward the optical element 120 asreceived light 128.

In some embodiments, at least a portion of the received light 128 may becoupled into the optical element 120 via the second end facet 108 ascoupled received light 130. The coupled received light 130 may be guidedwithin the optical element 120 toward an angled portion 110. In someembodiments, the angled portion 110 may be configured to reflect atleast a portion of the coupled received light 130 as reflected light132. In some embodiments, reflected light 132 may be directed in anout-of-plane direction with respect to a respective light propagationdirection (or vector) of the coupled emission light 124 and/or thecoupled received light 130.

FIGS. 1D-1F illustrate several different optical systems 140, 170, and180, which may describe different compact LIDAR systems that incorporateoptical light guide elements. Such LIDAR systems may be configured toprovide information (e.g., point cloud data) about one or more objects(e.g., location, shape, etc.) in a given environment. In an exampleembodiment, the LIDAR system could provide point cloud information,object information, mapping information, or other information to avehicle. The vehicle could be a semi- or fully-automated vehicle. Forinstance, the vehicle could be a self-driving car, an autonomous droneaircraft, an autonomous truck, or an autonomous robot. Other types ofvehicles and LIDAR systems are contemplated herein.

FIG. 1D illustrates an optical system 140, according to an exampleembodiment. The optical system 140 is one of a variety of differentoptical systems that may include light guides such as optical element100, as illustrated and described in reference to FIG. 1A. In an exampleembodiment, optical element 100 may be coupled to a transparentsubstrate 142. The optical element 100 may be coupled to a furthertransparent substrate 154 via an optical adhesive 156.

The optical system 140 may include a laser assembly that includes asubstrate 144, one or more elongate structures 146, and one or morelaser bars 148, each of which is coupled to a respective elongatestructure. In some embodiments, the substrate 144 may be coupled to thetransparent substrate 142 with an epoxy material 150. Additionally oralternatively, the substrate 144 and/or the elongate structures 146 maybe coupled to the further transparent substrate 154 via an epoxymaterial 152. Other ways to fix the one or more laser bars 148 to thetransparent substrate 142 are possible and contemplated herein.

The one or more laser bars 148 may be configured to emit light towards acylindrical lens 158, which may help focus, defocus, direct, and/orotherwise couple the emitted light into the optical element 100.

The optical system 140 may additionally or alternatively include afurther substrate 166. In some embodiments, a controller 168 and atleast one photodetector 167 may be coupled to the further substrate 166.Furthermore, the further substrate 166 can be coupled to the transparentsubstrate 142 via one or more light shields 164. In an exampleembodiment, the light shields 164 could be “honeycomb” type opticalbaffles or another type of opaque material. In such scenarios, thereflected light 132 may be detected by the at least one photodetector167. In some embodiments, the at least one photodetector 167 may includesilicon photomultipliers (SiPMs), avalanche photodiodes (APD), oranother type of photo sensors, which may be arranged in a linear orareal array.

In some embodiments, the optical system 140 may include an apertureplate 160, which may be coupled to the transparent substrate 142 and/orthe optical element 100 via an optical adhesive 162. In someembodiments, the optical adhesive 162 may be index-matched to an indexof refraction of the optical element 100, optical adhesive 156, and/orother elements of optical system 140. In some embodiments, the apertureplate 160 may include a plurality of apertures, which could be, forexample, openings or holes in a metal plate.

Furthermore, while FIG. 1D illustrates a single laser bar 148, a singleoptical element 100 and a single photodetector 167, it is understoodthat a plurality of such elements is possible and contemplated herein.For example, some embodiments may include 256 laser bars, 256 opticalelements, and a corresponding number of photodetectors.

FIG. 1E illustrates an optical system 170, according to an exampleembodiment. Optical system 170 may include similar or identical elementsas those of optical system 140 as illustrated and described in relationto FIG. 1D. In some embodiments, an optical element 100 b may be coupledto a transparent substrate 142. The optical element 100 b may beencapsulated or otherwise coupled to optical adhesive 172 and/or afurther transparent substrate 174. A filter 176 may be coupled to thefurther transparent substrate 174. The filter 176 may be configured tofilter wavelengths of light that are different from those emitted bylaser bar 148. That is, in an example embodiment, filter 176 may includea bandpass filter configured to pass emission light from the laser bar148.

In some embodiments, an aperture plate 178 may be coupled to thetransparent substrate 142. For example, the aperture plate 178 mayinclude a plurality of openings.

FIG. 1F illustrates an optical system 180, according to an exampleembodiment. The optical system 180 may include elements that are similaror identical to those of optical system 170, as illustrated anddescribed in relation to FIG. 1E. Furthermore, an aperture plate 182 maybe provided between a further transparent substrate 174 and the opticalelement 100.

In some embodiments, the photodetector 167 could include a complementarymetal-oxide semiconductor (CMOS) image sensor. Additionally oralternatively, the photodetector 167 may include at least one of asilicon photomultiplier (SiPM), a linear mode avalanche photodiode(LMAPD), a PIN diode, a bolometer, and/or a photoconductor. It will beunderstood that other types of photodetectors (and arrangements thereof)are possible and contemplated herein.

The controller 168 of optical systems 140, 170, and 180 includes amemory and at least one processor. The at least one processor mayinclude, for instance, an application-specific integrated circuit (ASIC)or a field-programmable gate array (FPGA). Other types of processors,computers, or devices configured to carry out software instructions arecontemplated herein. The memory may include a non-transitorycomputer-readable medium, such as, but not limited to, read-only memory(ROM), programmable read-only memory (PROM), erasable programmableread-only memory (EPROM), electrically erasable programmable read-onlymemory (EEPROM), non-volatile random-access memory (e.g., flash memory),a solid state drive (SSD), a hard disk drive (HDD), a Compact Disc (CD),a Digital Video Disk (DVD), a digital tape, read/write (R/W) CDs, R/WDVDs, etc.

In some embodiments, the optical systems 140, 170, and 180 may be LIDARsystems configured to provide information indicative of objects withinan environment of the optical system. As such, in some cases, theoptical systems 140, 170, and/or 180 may be disposed on a vehicle, suchas a self-driving car, a self-driving truck, a drone aircraft, and/or adrone boat. Other types of vehicles are possible and contemplatedherein.

III. Example Methods

FIGS. 2A-2K illustrate various blocks of a method of manufacture,according to one or more example embodiments. It will be understood thatat least some of the various blocks may be carried out in a differentorder than of that presented herein. Furthermore, blocks may be added,subtracted, transposed, and/or repeated. FIGS. 2A-2K may serve asexample illustrations for at least some of the blocks or steps describedin relation to methods 300 and 400 as illustrated and described inrelation to FIGS. 3 and 4, respectively. Additionally, some blocks ofFIGS. 2A-2K may be carried out so as to provide optical elements 100,100 a, 100 b, 120, and/or optical systems 140, 170, and 180, asillustrated and described in reference to FIGS. 1A-1F.

FIG. 2A illustrates a block 200 of a method of manufacture, according toan example embodiment. Block 200 includes preparing a photo-patternablematerial 204 on a transparent substrate 202. In some embodiments, thephoto-patternable material 204 may include a photoresist or any otherphoto-patternable material described herein. In such scenarios,preparing the photo-patternable material 204 may include depositingphotoresist by a spinning it onto the transparent substrate 202 followedby baking the photoresist.

In some embodiments, the transparent substrate 202 may include glass oranother transparent material. Furthermore, in some embodiments, thetransparent substrate 202 may be coupled to an opaque material 205. Theopaque material 205 may include an optical absorber material.

FIG. 2B illustrates a block 210 of a method of manufacture, according toan example embodiment. As illustrated, a mask 212 may be brought intoclose proximity or direct contact with the photo-patternable material204. Mask 212 may include a photolithography mask plate, a shadow mask,or another type of physical or virtual lithography mask. As an example,mask 212 may include opaque features 214 and transparent features 216.The combination of opaque features 214 and transparent features 216 maydefine various shapes or other features that may be transferred into thephoto-patternable material 204.

FIG. 2C illustrates a block 220 of a method of manufacture, according toan example embodiment. Block 220 includes causing a light source 221 toilluminate the mask 212 and at least a portion of the photo-patternablematerial 204 so as to expose at least a first feature 226. For example,the light source 221 may emit illumination light 222 by way of asubstantially uniform illumination intensity across the mask 212. Basedon the combination of opaque features 214 and transparent features 216,exposure light 224 may interact with the first feature 226 of thephoto-patternable material 204.

FIG. 2D illustrates block 230 and block 235 from a method ofmanufacture, according to example embodiments. Namely, blocks 230 and240 may illustrate cross-sectional profiles upon development ofrespective types of photo-patternable material. For example, block 230may occur in the case of using a positive-tone photo-patternable resist,while block 240 may occur in scenarios where a negative-tonephoto-patternable resist is used.

Referring to block 230, after exposure of first feature 226 anddevelopment of the photo-patternable material 204, the first feature 226may be removed to reveal a surface 234 of the transparent substrate 202.Furthermore, resist features 232 may remain after resist development.

Referring to block 240 (e.g., the negative-tone resist scenario), theremaining resist feature 236 may include the exposed first feature 226.Accordingly, after development, surfaces 238 may be revealed afterresist development.

It will be understood that other feature sizes, shapes, and contours arepossible. All other such alternatives are contemplated herein.

FIG. 2E illustrates a block 240 of a method of manufacture, according toan example embodiment. Block 240 includes causing light source 221 toilluminate a mask 212 and at least a portion of the photo-patternablematerial 204 so as to expose at least a first feature 246 as well as oneor more angled portions 245. As illustrated in FIG. 2E, the light source221 provide illumination light 242 that is incident at a non-normalangle with respect to a plane of the transparent substrate 204 and/orthe mask 212. In some embodiments, a slope angle of the angled portions245 may be based on an angle of the exposure light 244. For instance, inan example embodiment, a resulting structure (e.g., after photoresistdevelopment) could include a three-dimensional parallelogram shape.

While not illustrated in FIG. 2E, it will be understood that thelithography steps or blocks described herein may be provided usingimmersion lithography. That is, the mask 212 and the transparentsubstrate 202 could be submerged in a liquid with a refractive indexthat is different from that of air. In such a scenario, an angle ofincidence of the illumination light 242 may be different than the slopeangle of the angled portion 245 and the exposure light 244. For example,the angle of incidence of the exposure light 244 may be within aninclusive angle range between 15 to 45 degrees from normal incidence. Itwill be understood that other angles are possible and dynamicallyvarying angles of incidence of the illumination light 242 are possibleas well.

FIG. 2F illustrates a block 250 of a method of manufacture, according toan example embodiment. As illustrated in block 250, a position and/or anorientation 258 of the light source 221 may be adjusted (betweenexposures and/or dynamically during exposure) with respect to thetransparent substrate 202 and the mask 212. In such scenarios,respective incidence angles of the illumination light 252 and theexposure light 254 may be based on the orientation 258 of the lightsource 221.

Additionally or alternatively, a location and/or an orientation 259 ofthe transparent substrate 202 may be adjusted (between exposures and/ordynamically during exposure) with respect to the light source 221.

FIG. 2G illustrates a block 260 of a method of manufacture, according toan example embodiment. As illustrated, block 260 includes causing lightsource 221 to emit illumination light 270 so as to interact with a firstmask 262 and a second mask 268. Namely, first mask 262 may includeopaque features 264, which may be different in size, shape, and/ororientation as compared to opaque features 266 of the second mask 268.Upon interactions with the first mask 262 and the second mask 268,exposure light 272 may impinge on the photo-patternable material 204 soas to expose a first feature 274.

In some embodiments, the first mask 262, second mask 268, and exposurelight 272 may interact so as to provide a difference in light exposurealong the first feature 274. That is, in some cases, a first portion 275of the photo-patternable material 204 may be may be exposed with moreexposure light 272 than a second portion 276 of the photo-patternablematerial 204. In such scenarios, the different light exposure amountsmay be utilized to form the first feature 274. For example, it will beunderstood that analog, or grayscale, lithography may be applied so asto form the first feature 274.

FIG. 2H illustrates a block 280 of a method of manufacture, according toan example embodiment. Block 280 may include causing light source 221 toemit illumination light 288. The illumination light 288 may interactwith a first mask 262 and a third mask 282. The first mask 262 and thethird mask 282 may include respective opaque features 264 and 284.

Upon interaction with the first mask 262 and the third mask 282,exposure light 286 may impinge on at least a portion 289 of thephoto-patternable material 204. The portion 289 may include an angledportion 285.

FIG. 2I illustrates a block 290 of a method of manufacture, according toan example embodiment. Block 290 illustrates an elongate portion 292 ofthe photo-patternable material that remains following chemicaldevelopment of the resist. The elongate portion 292 may include anangled portion 293. It will be understood that block 290 could beconducted after one or more exposures as described herein. That is,block 290 may be performed after exposure with exposure light 224,exposure light 244, exposure light 254, exposure light 272, and/orexposure light 286. Furthermore, while block 290 illustrates a singlelayer of developed photo-patternable material, it will be understoodthat the elongate portion 292 may be provided using a plurality oflayers of photo-patternable materials and subsequent exposure anddevelopment steps. In other words, the elongate portion 292 may beprovided using multiple additive steps, such as building up multipleresist layers and conducting respective multiple exposure anddevelopment steps. Other ways to manufacture the elongate portion 292using semiconductor lithography techniques are possible and contemplatedherein.

FIG. 2J illustrates a block 294 of a method of manufacture, according toan example embodiment. As illustrated in FIG. 2J, a shadow mask 296 maybe aligned to correspond with the angled portion 293 of the elongateportion 292. Furthermore, metal 295 may be deposited through the shadowmask 296 so as to form an optically reflective surface on the angledportion 293. FIG. 2J illustrates metal 295 as being deposited along anormal or near-normal path with respect to the substrate 202. However,it will be understood that, other deposition orientations and otherconditions are possible. For example, metal could be deposited throughthe shadow mask 296 at an angle that is normal with respect to theangled portion 293. Other deposition angles are possible.

FIG. 2K illustrates a block 298 of a method of manufacture, according toan example embodiment. Block 298 illustrates the elongate portion 292 ofthe remaining photo-patternable material. The elongate portion 292includes an angled portion 293 that has been coated with a metal 295 soas to form a reflective surface. Namely, for light that is guided withinthe elongate portion 292, the metal 295 may be utilized so as to reflectlight out of a plane that includes the elongate portion 292.

FIG. 3 illustrates a method 300, according to an example embodiment.Method 300 may be carried out, at least in part, by way of some or allof the manufacturing steps or blocks illustrated and described inreference to FIGS. 2A-2K. It will be understood that the method 300 mayinclude fewer or more steps or blocks than those expressly disclosedherein. Furthermore, respective steps or blocks of method 300 may beperformed in any order and each step or block may be performed one ormore times.

Block 302 includes depositing a photoresist material on a substrate. Insome example embodiments, depositing the photoresist material on thesubstrate may include depositing a negative SU-8 resist on thesubstrate. The substrate could be a transparent material, such as glass.

Block 304 includes overlaying a first mask on the photoresist material.In some embodiments, the first mask defines a first feature. In suchscenarios, the first feature may be defined in either dark field orclear field tone. As an example, the first mask may include one or morerectangular openings or opaque features. It will be understood thatother shapes are possible and contemplated herein.

Block 306 includes causing a light source to illuminate the photoresistmaterial through the first mask during a first exposure. In such ascenario, the light source is positioned at a first angle, which caninclude a non-normal angle with respect to a plane parallel to thesubstrate.

In example embodiments, the light source may be optically coupled to acollimating lens. Furthermore, the light source may be an ultraviolet(UV) light source. The light source could part of a photolithographystepper or contact lithography system. Other types of photolithographysystems are contemplated and possible.

In some cases, method 300 may additionally include causing the lightsource to illuminate the photoresist material through the first maskduring a second exposure. In such scenarios, the second exposure mayinclude the light source being positioned at a second angle with respectto the plane parallel to the substrate.

Additionally or alternatively, some embodiments of method 300 mayinclude, while causing the light source to illuminate the photoresistmaterial through the first mask (e.g., during the first exposure or thesecond exposure), adjusting a position of the substrate with respect tothe light source. That is, while exposing the photoresist, the method300 may include: 1) moving the light source with respect to a fixedposition of the first mask and substrate; 2) moving the first mask andsubstrate with respect to a fixed position of the light source; or 3)moving the light source as well as the first mask and substrate.

In some embodiments, the method 300 may additionally or alternativelyinclude immersing the substrate and the photoresist material in a bath.Such a bath may include a liquid such as water or another type of fluid.In such scenarios, causing the light source to illuminate thephotoresist material could include causing the light source toilluminate the photoresist material through at least a portion of theliquid. It will be understood that a variety of different immersionlithography techniques are possible within the context of the presentdisclosure. All other such immersion lithography techniques arecontemplated herein.

Although embodiments herein are described in reference tophotolithography by large area exposure, it will be understood that thedefinition of the optical elements, angled portion, and other structuresherein may be provided using, among other techniques, direct writelithography techniques, such as laser direct writing and/or electronbeam lithography. All such other techniques are possible andcontemplated herein.

Block 308 includes developing the photoresist material so as to retainan elongate portion of the photoresist material on the substrate. Forexample, a first end of the elongate portion could include an angledportion. The angled portion can be sloped at an angle with respect to along axis of the elongate portion.

In some embodiments, the elongate portion could be utilized as a lightguide manifold. In such scenarios, method 300 may optionally includecoupling an aperture plate to the light guide manifold. For example, theaperture plate may include at least one aperture. The at least oneaperture can be optically coupled to the light guide manifold. In somescenarios, the aperture plate can be coupled to a distal end of thelight guide manifold. As such, method 300 may additionally includecoupling a light-emitter device to a proximal end of the light guidemanifold.

Block 310 includes overlaying a second mask on the developed photoresistmaterial. In such scenarios, the second mask defines a second featurecorresponding to the angled portion. The second mask could include, forexample, a shadow mask with one or more openings defining square orrectangular regions corresponding to the angled portion. In an exampleembodiment, the shadow mask could include one opening for each elongateportion of the photoresist material on the substrate. In such ascenario, the shadow mask could be aligned and then clamped to thesubstrate prior to metal deposition.

Block 312 includes depositing a reflective material through the secondmask onto the angled portion. In some embodiments, the reflectivematerial may include a metal that is optically-reflective in anear-infrared wavelength range. For example, the metal could includetitanium, platinum, gold, silver, aluminum, tungsten, or another type ofmetal, applied individually or in combination.

In other embodiments, overlaying the second mask could include using aphotolithography mask plate as part of a second lithography step to formone or more openings in a further layer of photoresist. According toblock 312, the reflective material could be deposited through the secondmask and the further layer of photoresist could be subsequently removedin a metal lift-off process. It will be understood that other ways touse a shadow or photolithography mask so as to deposit or otherwise formthe reflective material along the angled portion are possible andcontemplated herein.

FIG. 4 illustrates a method 400, according to an example embodiment.Method 400 may be carried out, at least in part, by way of some or allof the manufacturing steps or blocks illustrated and described inreference to FIGS. 2A-2K. It will be understood that the method 400 mayinclude fewer or more steps or blocks than those expressly disclosedherein. Furthermore, respective steps or blocks of method 400 may beperformed in any order and each step or block may be performed one ormore times.

Block 402 includes depositing a photoresist material on a substrate. Insome embodiments, depositing the photoresist material on the substratemay include depositing a negative SU-8 resist on the substrate.

Block 404 includes overlaying a first mask on the photoresist material.In such scenarios, the first mask defines a first feature. As describedelsewhere herein, the first mask could include a photomask, a maskplate, a shadow mask, or another type of physical or virtuallithographic mask.

Block 406 includes overlaying a second mask on the first mask. In suchcases, the second mask defines a second feature. In other words, thesecond mask could be a photomask that defines at least one differentfeature from that of the first mask.

Block 408 includes causing a light source to illuminate the photoresistmaterial through the first mask and the second mask. The light source ispositioned at a first angle. The first angle forms a non-normal anglewith respect to a plane parallel to the substrate.

In some embodiments, while causing the light source to illuminate thephotoresist material through the first mask and the second mask, themethod 400 may include adjusting a position of the substrate withrespect to the light source. Additionally or alternatively, whilecausing the light source to illuminate the photoresist material throughthe first mask and the second mask, method 400 could include adjusting aposition of the light source with respect to the substrate.

Block 410 includes removing the second mask. The second mask could beremoved by physically moving it away from the first mask and thesubstrate.

Block 412 includes overlaying a third mask on the first mask. The thirdmask defines a third feature. In other words, the third mask may definefeatures that are at least in part different from the first and/orsecond features.

Block 414 includes causing the light source to illuminate thephotoresist material through the third mask and the first mask. In someembodiments, causing the light source to illuminate the photoresistmaterial through the third mask and the first mask may include asubsequent exposure. During the subsequent exposure, the light sourcecould be positioned at a second angle with respect to the plane parallelto the substrate.

In some cases, while causing the light source to illuminate thephotoresist material through the third mask and the first mask, themethod 400 may include adjusting a position of the substrate withrespect to the light source. Additionally or alternatively, whilecausing the light source to illuminate the photoresist material throughthe third mask and the first mask, method 400 could include adjusting aposition of the light source with respect to the substrate.

Block 416 includes developing the photoresist material so as to retainan elongate portion of the photoresist material on the substrate. Afirst end of the elongate portion includes an angled portion, which issloped at an angle with respect to a long axis of the elongate portion.

In some embodiment, the elongate portion may include a light guidemanifold. In such cases, method 400 may include coupling an apertureplate to the light guide manifold. The aperture plate could include aplurality of apertures. At least one aperture of the plurality ofapertures could be optically coupled to the light guide manifold. Forexample, in the case where the substrate includes a plurality of lightguide manifolds, each aperture opening may correspond to a respectiveoutput facet of a given light guide manifold. The aperture plate may beformed of metal or another optically-opaque material.

In some embodiments, the aperture plate is coupled to a distal end ofthe light guide manifold. In such scenarios, the method 400 additionallyor alternatively could include coupling a light-emitter device to aproximal end of the light guide manifold.

Block 418 includes overlaying a fourth mask on the developed photoresistmaterial. In such a scenario, the fourth mask defines a fourth featureto correspond to the angled portion.

Block 420 includes depositing a reflective material through the fourthmask onto the angled portion. In such scenarios, the reflective materialmay include a metal that is optically-reflective in a near-infraredwavelength range.

The particular arrangements shown in the Figures should not be viewed aslimiting. It should be understood that other embodiments may includemore or less of each element shown in a given Figure. Further, some ofthe illustrated elements may be combined or omitted. Yet further, anillustrative embodiment may include elements that are not illustrated inthe Figures.

A step or block that represents a processing of information cancorrespond to circuitry that can be configured to perform the specificlogical functions of a herein-described method or technique.Alternatively or additionally, a step or block that represents aprocessing of information can correspond to a module, a segment, aphysical computer (e.g., a field programmable gate array (FPGA) orapplication-specific integrated circuit (ASIC)), or a portion of programcode (including related data). The program code can include one or moreinstructions executable by a processor for implementing specific logicalfunctions or actions in the method or technique. The program code and/orrelated data can be stored on any type of computer readable medium suchas a storage device including a disk, hard drive, or other storagemedium.

The computer readable medium can also include non-transitory computerreadable media such as computer-readable media that store data for shortperiods of time like register memory, processor cache, and random accessmemory (RAM). The computer readable media can also includenon-transitory computer readable media that store program code and/ordata for longer periods of time. Thus, the computer readable media mayinclude secondary or persistent long term storage, like read only memory(ROM), optical or magnetic disks, compact-disc read only memory(CD-ROM), for example. The computer readable media can also be any othervolatile or non-volatile storage systems. A computer readable medium canbe considered a computer readable storage medium, for example, or atangible storage device.

While various examples and embodiments have been disclosed, otherexamples and embodiments will be apparent to those skilled in the art.The various disclosed examples and embodiments are for purposes ofillustration and are not intended to be limiting, with the true scopebeing indicated by the following claims.

What is claimed is:
 1. A method comprising: depositing a photoresistmaterial on a substrate; overlaying a first mask on the photoresistmaterial, wherein the first mask defines a first feature; causing alight source to illuminate the photoresist material through the firstmask during a first exposure, wherein the light source is positioned ata first angle, wherein the first angle comprises a non-normal angle withrespect to a plane parallel to the substrate; developing the photoresistmaterial so as to provide an optical element including retaining anelongate portion of the photoresist material on the substrate, wherein afirst end of the elongate portion comprises an angled portion, andwherein the angled portion is sloped at an angle with respect to a longaxis of the elongate portion; overlaying a second mask on the developedphotoresist material, wherein the second mask defines a second featurecorresponding to the angled portion; and depositing a reflectivematerial through the second mask onto the angled portion, wherein theoptical element includes a first light guide portion and a second lightguide portion, a first end facet and a second end facet, wherein lightcoupled via the first end facet into the first light guide portion ascoupled emission light is outcoupled to an environment via the secondend facet and after reflection or redirection is coupled via the secondend facet as coupled received light, guided within the second lightguide portion toward the angled portion, and reflected by the angledportion as reflected light in an out-of-plane direction with respect toa respective light propagation direction or vector of the coupledemission light and/or the coupled received light.
 2. The method of claim1, wherein the light source is optically coupled to a collimating lens.3. The method of claim 1, further comprising: immersing the substrateand the photoresist material in a bath, wherein the bath comprises aliquid, wherein causing the light source to illuminate the photoresistmaterial comprises causing the light source to illuminate thephotoresist material through at least a portion of the liquid.
 4. Themethod of claim 1, further comprising: causing the light source toilluminate the photoresist material through the first mask during asecond exposure, wherein the second exposure comprises the light sourcebeing positioned at a second angle with respect to the plane parallel tothe substrate.
 5. The method of claim 1, further comprising: whilecausing the light source to illuminate the photoresist material throughthe first mask, adjusting a position of the substrate with respect tothe light source.
 6. The method of claim 1, further comprising: whilecausing the light source to illuminate the photoresist material throughthe first mask, adjusting a position of the light source with respect tothe substrate.
 7. The method of claim 1, wherein the elongate portioncomprises a light guide manifold, wherein the method further comprise:coupling an aperture plate to the light guide manifold, wherein theaperture plate comprises at least one aperture, wherein the at least oneaperture is optically coupled to the light guide manifold, andoptionally wherein the aperture plate is coupled to a distal end of thelight guide manifold, wherein the method further comprises: coupling alight-emitter device to a proximal end of the light guide manifold.
 8. Amethod comprising: depositing a photoresist material on a substrate;overlaying a first mask on the photoresist material, wherein the firstmask defines a first feature; overlaying a second mask on the firstmask, wherein the second mask defines a second feature; causing a lightsource to illuminate the photoresist material through the first mask andthe second mask, wherein the light source is positioned at a firstangle, wherein the first angle comprises a non-normal angle with respectto a plane parallel to the substrate; removing the second mask;overlaying a third mask on the first mask, wherein the third maskdefines a third feature; causing the light source to illuminate thephotoresist material through the third mask and the first mask during aninitial exposure; developing the photoresist material so as to providean optical element including retaining an elongate portion of thephotoresist material on the substrate, wherein a first end of theelongate portion comprises an angled portion, and wherein the angledportion is sloped at an angle with respect to a long axis of theelongate portion; overlaying a fourth mask on the developed photoresistmaterial, wherein the fourth mask defines a fourth feature to correspondto the angled portion; and depositing a reflective material through thefourth mask onto the angled portion, wherein the optical elementincludes a first light guide portion and a second light guide portion, afirst end facet and a second end facet, wherein light coupled via thefirst end facet into the first light guide portion as coupled emissionlight is outcoupled to an environment via the second end facet and afterreflection or redirection is coupled via the second end facet as coupledreceived light, guided within the second light guide portion toward theangled portion, and reflected by the angled portion as reflected lightin an out-of-plane direction with respect to a respective lightpropagation direction or vector of the coupled emission light and/or thecoupled received light.
 9. The method of claim 8, further comprising:causing the light source to illuminate the photoresist material throughthe third mask and the first mask, wherein the light source ispositioned at a second angle with respect to the plane parallel to thesubstrate during a subsequent exposure.
 10. The method of claim 8,further comprising: while causing the light source to illuminate thephotoresist material through the first mask and the second mask,adjusting a position of the substrate with respect to the light source.11. The method of claim 8, further comprising: while causing the lightsource to illuminate the photoresist material through the third mask andthe first mask, adjusting a position of the substrate with respect tothe light source.
 12. The method of claim 8, further comprising: whilecausing the light source to illuminate the photoresist material throughthe first mask and the second mask, adjusting a position of the lightsource with respect to the substrate, or while causing the light sourceto illuminate the photoresist material through the third mask and thefirst mask, adjusting a position of the light source with respect to thesubstrate.
 13. The method of claim 8, wherein depositing the photoresistmaterial on the substrate comprises depositing a negative SU-8 resist onthe substrate.
 14. The method of claim 8, wherein the reflectivematerial comprises a metal that is optically-reflective in anear-infrared wavelength range.
 15. The method of claim 8, wherein theelongate portion comprises a light guide manifold, wherein the methodfurther comprises: coupling an aperture plate to the light guidemanifold, wherein the aperture plate comprises at least one aperture,wherein the at least one aperture is optically coupled to the lightguide manifold, and optionally wherein the aperture plate is coupled toa distal end of the light guide manifold, wherein the method furthercomprises: coupling a light-emitter device to a proximal end of thelight guide manifold.
 16. A method comprising: depositing a photoresistmaterial on a substrate; overlaying a first mask on the photoresistmaterial, wherein the first mask defines a first feature; causing alight source to illuminate the photoresist material through the firstmask during a first exposure, wherein the light source is positioned ata first angle, wherein the first angle comprises a non-normal angle withrespect to a plane parallel to the substrate; causing the light sourceto illuminate the photoresist material through the first mask during asecond exposure, wherein the light source is positioned at a secondangle, wherein the second angle comprises a substantially normal anglewith respect to the plane parallel to the substrate; developing thephotoresist material so as to retain an elongate portion of thephotoresist material on the substrate, wherein a first end of theelongate portion comprises an angled portion, wherein the angled portionis sloped at an angle with respect to a long axis of the elongateportion, and wherein a second end of the elongate portion that isopposite to the first end comprises an endface that is substantiallynormal to the long axis of the elongate portion; overlaying a secondmask on the developed photoresist material, wherein the second maskdefines a second feature corresponding to the angled portion; anddepositing a reflective material through the second mask onto the angledportion.
 17. The method of claim 16, wherein the light source isoptically coupled to a collimating lens.
 18. The method of claim 16,further comprising: immersing the substrate and the photoresist materialin a bath, wherein the bath comprises a liquid, wherein causing thelight source to illuminate the photoresist material comprises causingthe light source to illuminate the photoresist material through at leasta portion of the liquid.
 19. The method of claim 16, further comprising:while causing the light source to illuminate the photoresist materialthrough the first mask, adjusting a position of the substrate withrespect to the light source.
 20. The method of claim 16, furthercomprising: while causing the light source to illuminate the photoresistmaterial through the first mask, adjusting a position of the lightsource with respect to the substrate.